Ballast tube



March 8, 1960 B. F. STEIGER ET AL 2,923,061

BALLAST TUBE Filed Oct. 18, 1956 BENJAMIN F. STEIGER MAX YARMOVSKY INVENTORS ATTORNEY United States Patent BALLAST TUBE Benjamin F. Ste-iger, Summit, and Max Yarmovsky, Livingston, N.J., assignors, by mesne assignments, to Tung- Sol Electric Inc., Newark, NJ., a corporation of Delaware Application October 18, 1956, Serial No. 616,850

Claims. (Cl. 338-20) This invention relates to a ballast tube having an improved filament which provides better operating conditions and longer life.

Ballast tubes containing an iron wire filament in an atmosphere of hydrogen at reduced pressure have been used for many years to provide a stabilized constant cur rent for other circuit components. It is well-known that iron wire has a temperature coefficient of resistivity such that, over an appreciable range of applied voltage, the current through the wire is substantially independent of the voltage drop across it; The construction and operation of ballast tubes have'been described in an article by H. A. Jones in the General Electric Review for May 1925.

Ballast tubes made of pure iron wire have several in- The present invention comprises a ballasttube having a life which is at least three times the life of prior ballast tubes. No hot spots are developed on the filament and the distortion of the wire is greatly reduced, thereby retaining the resistance and constant current characteristics within a small range of values. l

One of the objects of this invention is to provide an improved ballast tube which avoids one or more of the disadvantages and limitations of prior art tubes.

Another object of the invention is to increase the life of ballast tubes.

Another object of the invention is to retain the operating characteristics of a ballast tube during its life.

Another object of the invention is to eliminate hot spots on the filament.

Another object of the invention is to reduce the filament distortion during the useful life of the tube. The invention comprises a ballast tube having an en-.

velope in which an iron Wire is mounted on insulating supports. Lead-in conductors are connected to the iron wire for connection to an external circuit. The iron wire is plated with a thin film of gold and the envelope is filled with an atmosphere of hydrogen at a reduced pres 2,928,061 7 Patented Mar. 8, .1960

Fig. 3 is a detailed view, greatly enlarged, of a portion of the ballast tube showing the insulator plate, the iron wire, and one of the supporting wires.

Fig. 4 is a cross sectional view, greatly enlarged, showing the gold plated iron wire.

Fig. 5 is a cross sectional view similar to Fig. 4 taken along line 5-5 of that figure.

Referring now to Figs. 1, 2 and 3, the ballast tube includes an envelope 10 supported on a base 11 which contains a plurality of contact pins 12 for connection with an external circuit. On theinside of the envelope, an iron wire 13 is mounted on insulating disks 14 and 15. These disks are generally held in position by one or more heavy supporting wires 16 although any other type of supporting means may be employed. In the example shown, a grommet 17 is employed to grip the insulating disks 14 and 15, these grommets having small fins 18 which may be soldered or welded to the supporting wires 16.

ice

The iron wire as indicated in Figs. 4 and 5 is plated with a thin covering of gold 19. The thickness of the plating is such that the weight of the wire is increased about six percent. Experimental ballast tubes made in the laboratory used iron wire of at least 99.85 percent purity. The gold plating consisted of 24 carat gold.

When this wire is mounted in its envelope, the envelope is filled with hydrogen at about twice the pressure of prior art tubes; that is, about 12 millimeters of mercury. The increased pressure causes an increased heat conduction from the filament to the envelope walls but this additional dissipation of heat is counteracted by the reduced radiation characteristics of the gold surface.

Ballast tubes manufactured in accordance with the above described characteristics have exceptional long life (in many cases over 4,000 hours) and are not subjected to changing characteristics due to hot spots or other filament changes. I

The foregoing disclosure and drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense. The only limitations are to be determined from the scope of the appended claims. I

We claim: Y

1. A ballast tube which passes constant current for a range of applied voltages comprising; an envelope and a gold-plated iron wire within the envelope in an atmosed within the envelope, lead-in conductors connected to the iron wire for external connection, and a film of gold surrounding the iron wire.

3. A ballast tube which passes constant current for a range of applied voltages comprising: an envelope, an iron wire mounted Within the envelope in an atmosphere of hydrogen at a pressure of more than 10 millimeters of mercury, said iron wire covered with a film of gold, and lead-in conductors connected to the iron wire for connection to an external circuit.

4. A ballast tube which passes constant current for a restricted range of applied voltages comprising: an envelope, an iron wire mounted within the envelope in an atmosphere of hydrogen, said iron wire covered with a film of gold, the thickness of the gold film being such that the weight of the wire is increased about six percent.

5. A' ballast tube which passes constant current for a restricted range of applied voltages comprising: an envelope, an iron wire mounted within the envelope in an atmosphere of hydrogen at a pressure of more than 10 millimetersof mercury, said iron wire covered with a cent, and 'lead-in'tqnduetprs opnnected'to the iron wire 1,945,726 for cbnnetibn to an external circuit. v r 2,047,351 2,092,133 References Cited m the file of this patent ,154 2 I UNITED STATES PATENTS; 6 2,530, 743,028 Potter NOV. 3, 1908 1,083,070 Eldred Dec. 30, 1913 1,101,821 Van Aller June 30, 1914 Jones May 5, 1931" A 523 Brockway Feb. 6, 1934 Alexander July 14, 1936 Neumann Sept. 7, 1937 Olshevsky -.L Apr. 18, 1939 De Graaflf Nov. 21, 1950 OTHER REFERENCES Wireless World, November 15, 1935, pages 522 and 

5. A BALLAST TUBE WHICH PASSES THROUGH CURRENT OR A RESTRICTED RANGE OF APPLIED VOLTAGE COMPRISING: AN ENVELOPE, AN IRON WIRE MOUNTED WITHIN THE ENVELOPE IN AN ATMOSPHERE OF HYDROGEN AT A PRESSURE OF MORE THAN 10 MILLIMETERS OF MERCURY, SAID IRON WIRE COVERED WITH A FILM OF GOLD, THE THICKNESS OF THE GOLD FILM BEING ABOUT SUCH THAT THE WEIGHT OF THE WIRE IS INCREASED ABOUT SIX PERCENT, AND LEAD-IN CONDUCTORS CONNECTED TO THE IRON WIRE FOR CONNECTION TO AN EXTERNAL CICRUIT. 